It is known that siloxanes can be combined with organic polymers using conventional polymerization techniques, such as radical polymerization, polycondensation or polyaddition.
Moreover, it is possible, for example, to prepare silicon-containing polymers having a comb structure, which have organopolysiloxanes as the main chain and vinyl polymers as side chains, in a manner such that in a first process step vinyl monomers, such as acrylates or methyacrylates are polymerized in the presence of mercaptosilanes having dialkoxysilyl groups, with the formation of macromers (prepolymers), which are subsequently polycondensed in a second process step alone or combined with dialkoxysilanes in the presence of condensation catalysts, such as metal salts or amines (cf. EP-A2-205, 096). Here, the vinyl monomers are initially polymerized and terminally linked via an S-bridge with the dialkoxysilane radical and the difunctional silane derivatives thus formed are then polycondensed. In other words, the side chains or teeth of the comb are initially formed, which are then linked with the main chain formed by polycondensation.
In a similar manner, block copolymers having polysiloxane segments can be obtained in a first process step, for example, by polymerizing acrylic monomers in the presence of mercaptans having hydroxyl groups or carboxyl groups with the formation of prepolymers, which are then polycondensed in a second process step with bifunctional polysiloxanes in the presence of condensation catalysts (cf. EP-A2-235,728).
Moreover, graft copolymers having a block structure are known in which block copolymers are prepared in a first process step by polycondensation from polysiloxanes and organic homopolymers or copolymers in which each are bifunctional; and in a second process step, monomeric acrylic compounds are radically grafted onto the graft bases thus obtained in the presence of free radical forming initiators (cf. DE-A1-36 06 982).
Also, organosilicon block polymers are known in which polydiorganosiloxanes having terminal Si--H bonds are reacted in a first process step with selected, aliphatically unsaturated organosilyl-substituted acrylic pinacols in the presence of platinum catalysts; then, in a second process step, vinyl monomers, such as acrylate compounds, are thermally graft copolymerized onto the siloxane prepolymers thus formed, which contain bis(silyl pinacolate) radicals arranged in terminal positions or along the chain, in which the bis(silyl pinacolate) radicals function as free radical forming initiators and the graft copolymerized acrylate radicals are bonded to the siloxane graft base via Si--O bonds. These are known to be susceptible to hydrolysis (cf. DE-A1-37 07 399).
According to the prior art, monomeric vinyl compounds, which include monomeric acrylic compounds, can either be polymerized before linking with a siloxane base or can be graft copolymerized onto a siloxane base, by the radical mechanism. Since the polymers having a high molecular weight, but a very wide molecular weight distribution are obtained by radical polymerization, the resultant products also consist of mixtures of very different copolymers, in which polyorganosiloxanes having short chain polyacrylates have a silicon character and polyorganosiloxanes with long chain polyacrylates have a polyacrylate character. Therefore, comb or block structured poly(organo-organosiloxanes) having specific arrangement and relatively uniform chain length of the individual combs and blocks cannot be prepared in this manner.
Therefore, it is an object of the present invention to provide poly(organo-organosiloxanes) having comb or block structures, in which the individual combs and blocks are present in a specific arrangement with relatively uniform chain lengths and are linked to the polysiloxane base via hydrolysis-resistant bonds. Another object of the present invention is to provide processes for preparing poly(organo-organosiloxanes), in which monomeric compounds, which have a C--C double bond in the .alpha.-position relative to a carbonyl group or nitrile group, are graft copolymerized onto a siloxane base or these monomeric compounds are initially polymerized and subsequently linked to the siloxane base.